Control system



July 22, 1941. w. SCHAELCHLIN CONTROL SYSTEM Filed Sept. 27. 1940 DrgueWITNESSES: 7 INVENTOR Wa/Zer Scfme/cfi/m BY 7 M E ,W k ATTORNEY PatentedJuly 22, 1941 ,con'rnor. SYSTEM Walter Scbaelchlin, Wilklnsbnrg, Pa.,asaignor to Westinghouse Electric 80 Manufacturing Company, EastPittsburgh, Pa., a corporation of Pennsylvania Application September 27,1940, Serial No. 358,632

9 Claims.

in the lowering direction, so that for any controller setting, anincrease in load will cause a drooping speed-torque characteristic whenthe motor overhauls in the lowering direction.

Another object of my invention is to provide a simple and inexpensivebut highly reliable control system for a hoist motor. 1

Still another object of my invention is to provide means for maintainingthe hoist motor under positive and safe control at all times.

Other objects and advantages will become more apparent from a study ofthe following specification when considered in conjunction with theaccompanying drawing, in which:

Figure l. is a schematic showing oi a control system embodying theprinciples of my invention; and

Figs. 2 and 3 arespeed-torque characteristics 4 for lowering andhoisting, respectively, of the hoist motor.

Referring more particularly to Fig. 1, a variable voltage controlsystem. including a genera,

tor G and a motor M energized thereby, is provided (the prime mover forthe generator not being shown). The generator has a series field it, aseii excited field winding it and a separately excited field 32, whereasthe motor has a series Winding i3 and a separately excited iieid windingi i. The respective separate field windings are excited by aciirectwurrent source of potential indicated by and.

inyenticn may best he described by refer ring to the detailed operationof the circuit shown in Fig. to the No. i hoist position, a circuit iscompleted through controller contact member a by virtue of the movementof the adjacent controller segment which wili complete an energizingcircuit when the controller 0 is moved through the coil of relay l5,thereby causing opening of contact members It and interruption of thenormal shunt circuit through the dynamic braking resistor i'l. It willbe noted that this;

circuit is completed throughout not only the hoisting operation, butalso the lowering operation.

Another energizing circuit will be completed 7 through the controllercontact member 0, which will effect actuation of relay I8 and closing ofcontact member is. This will effect completion of a circuit through themotor series field wind.- ing l 3, which results in the inclusion of themotor series field winding in the main series circuit including themotor and generator armatures. Another energizing circuit is completedthrough controller contact member e, which will eiiect energization ofthe hoisting relay 32, which is so called because it completes anenergizing circuit which efl'ects current flow through the generatorseparate field winding i2 insuch di motion as to efiect hoistingoperation oi the motor.

As the controller C is moved to the second, third, fourth, fifth andsixth hoist positions, suecessive energizing circuits will he completedthrough controller contact members h, Lit and m, which will effectsuccessive operation of relays 20, 2t, 22, 23 and 24. Successiveoperation of relays 20, El and 22 will effect progressive shunting oflarger and larger portions of re sister 25 in series with the generatorshunt field winding 92, which will effect gradual strength"- ening oithe generator field winding it; Fol towed by this, the operation ofrelay 23 will efiect insertion of the self-excited generator held windingii in shunt circuit with the generator erma ture which is followed bythe operation re-leg it, which eiiects shunting of the lower portion ofresistor 28 having the effect of strengthen ing the generator selfexcited field winding it, It will be noted that relay 2! remains deenerglued during the hoisting operation; therefore, the generator seriesfield winding ii) remains in terrupted and is excluded from the circuit.

In other words, during the hoisting operation, the main circuit includesthe generator inc torarrnatures and the motor series field wind ing it.This results in operation of motor hi as a compound motor during thehoisting opera 7 tion. which motor is, oi course, receiving power fromthe generator. The motor wilt have speed torque characteristics duringthe hoisting opera,

tion as shown in Fig. 3; namely, for each of the 6 positions oi thecontroller during hoisting operation there is a separate droopingspeed-torque curve which indicates that with increasing iced or torquethe speed of the motor will decrease, which is highly satisfactoryduring hoisting.

If the controller were suddenly reversed and thrown into the firstlowering position, there would be an energizing circuit completedthrough the controller contact member 2), effecting energization ofrelay 9, which effects strengthening of the motor field winding 14.Another energizing circuit would be completed through controller contactmember d which will effect energization oi relay 21 and closing ofcontact members 28, which effects insertion of the generator seriesfield winding 10, together with a stabilizing resistor 29 in the mainseries circuit including the motor and generator armatures.

Another energizing circuit will be 'completed through controller contactmember I which will effect energization of the lowering relay 30, whichwill reverse the direction of energizing current fiow through theseparate field winding 12 (hoisting relay 32 now being deenergized),thereby efiecting reversal of rotation of motor M. As the controller ismoved to the 2nd, 3rd, 4th, 5th and 6th lowering positions, it willeffect the same successive operation of relays 20, 2t, 22 and 23 as inthe case or" the hoisting operation so as to at first effectstrengthening of the generator field winding i2, followed by theinsertion of the self-excited field ii and a strengthening thereof bythe shunting of the lower portion of resistor 26.

For these successive lowering positions of the controller, speed torquecharacteristics will be obtained such as shown in Fig. 2, whichpartially shows the motoring characteristic during lowering (in dottedlines), and which shows the over hauling characteristic (in full lines)during lowerlng. 0f outstanding significance is the fact that foroverhauling operation in the lowering direction, each of thespeed-torque curves for the various controller positions 1 to 6inclusive, has drooping characteristic. other words, in going fromno-load to an increasingly heavier load, the speed will graduallydecrease instead of increase as is usually the case in conventionalhoist operation. This decrease in speed with increase in load is highlyadvantageous since it provides more positive control for heavy loads,which is very desirable in hoist operation.

It will be noted that during the lowering oporation, the motor seriesfield winding 13 is cut out of the circuit because relay l5 remainsdeenergized and contact member iii is held closed by spring 35. When themotor is lowering an empty hook, the generator series field is additive,thereby insuring good acceleration of the separately excited hoistmotor. When the motor is lowering also the generator series field duringthe motor operation is cumulative, but when the motor begins tooverhaul, the generator series field becomes differential and therebyreduces thegenerator voltage as the load increases. The action of theself-excited fields tends to emphasize this feature. I have thussucceeded in providing a very simple control system which will give adrooping speed-torque curve for an overhauling lowering load which isideal in the operation of a hoist, and which is very diillcult to securewith the other types of hoist control.

When controller C is moved to the "01 position, all of the fieldwindings are deenergized. At the same time, the spring closed contactmember IE will cause dynamic braking by connecting the motor armatureand motor series held 13 across the dynamic braking resistor l1.

It will be noted that in the event of power fail ure, dynamic braking isalso insured during overhauling operation since the polarity of theresidual magnetism is always in the right direction.

I am, of course, aware that others, particularly after having had thebenefit of the teachings of. my invention, may devise other systems ofcontrol embodying my invention, and I, therefore, do not wish to belimited to the specific showings made in the drawing and the descriptivedisclosure hereinbefore made, but wish to be limited only by the scopeof the appended claims and such prior art that may be pertinent.

I claim as my invention:

1. A hoist motor control system comprising, in combination, a variablevoltage system including a generator and a motor energized thereby, saidgenerator and motor each having shunt and series field windings, asource of energizing potential, circuit means including a reversingcontroller between said source and one of said field windings foreffecting reversal of said motor and switching means for including themotor series field winding in the main motor circuit during hoisting andfor excluding said motor series field winding during lowering operationthereby obtaining a drooping speed-torque characteristic for said motorduring overhauling in the lowering direction.

2. A hoist motor control system comprising, in combination, a variablevoltage system including a generator and a motor energized thereby, saidgenerator and motor each having shunt and series field windings, asource of energizing potential, circuit means including a reversingcontroller between said source and one of said field windings forefl'ecting reversal of said motor and switching means for including themotor series field winding and excluding the generator series fieldwinding in the main motor circuit during hoisting and for including thegenerator series field winding and excluding said motor series fieldwinding during lowering operation thereby obtaining a droopingspeed-torque characteristic for said motor during overhauling in thelowering direction.

3. A hoist motor control system comprising, in combination, a variablevoltage system including a generator and a motor energized thereby, saidgenerator and motor each having shunt and series field windings, saidgenerator also having a self excited field winding, a source ofenergizing potential, circuit means including a reversing controllerbetween said source and the generator shunt field and separately excitedfield windlngs for effecting reversal of said motor and switching meansfor including the motor series field winding and excluding the generatorseries field winding in the main motor circuit during hoisting and forincluding the generator ser es field winding and excluding said motorseries field winding during lowering operation thereby obtaining adrooping speed-torque characteristic for said motor during overhaulingin the lowering direction.

,4. A hoist motor control system comprising, in combination, a variablevoltage system including a generator and a motor energized thereby, saidgenerator and motor each having shunt and series field windings, asource of energizing potential, circuit means including a reversingcontroller between said source and one 01 said field windings foreffecting reversal of said motor and winding, an external sourceswitching means for including successive steps of resistance in circuitrelationship with said last mentioned field winding in either thehoisting or lowering operation and for including the motor series fieldwinding in the main motor circuit during hoisting and for excluding saidmotor series field winding during lowering operation thereby obtaining adrooping speed-torque characteristic for said motor during overhaulingin the lower direction for any given setting of said controller.

motor comprising, incombination, a generator and motor each having aseries field winding and a separately excited shunt field winding, saidgenerator also having a self-excited shunt field winding, an externalsource of energization for said separately excited windings, reversingswitch means for reversing the direction of said energization andincluding contact members for selectively connecting the motor andgenerator armatures in series with the motor series field winding or thegenerator series field winding depending on whether said reversingswitch means is thrown in the hoisting or lowering direction,respectively, thereby obtaining a drooping speed-torque characteristicfor said motor while overhauling in the lowering direction forincreasing torque loads,

'1. A variable voltage control system for a hoist motor comprising, incombination, a generator and motor each having a series field windingand a separately excited shunt field winding, said generator also havinga sell excited shunt field oi energization for said separately excitedwindings, reversing switch field winding in either the hoisting orlowering operation and for reversing the direction of said energizatlonand including contact members for selectively connecting the motor andgenerator armatures in series with the motor series field winding or thegenerator series field winding depending on whether said reversingswitch means is thrown in hoisting or lowering direction, respectively,thereby obtaining a drooping speed-torque" characteristic for said motorwhile overhauling in the lowering direction for increasing torque loadsfor any given setting of said controller.

8. A variable voltage control system for a hoist motor comprising, incombination, a generator and motor each having a series field winding,an external source of energization for said generator, reversing switchmeans for reversing the direction of said energization'and includingcontact members for selectively connecting or disconnecting saidgenerator series iield winding from series circuit relationship with themotor and generator armatur'es depending upon whether said reversingswitch means is thrown in the lowering or hoisting direction,respectively, so as to impart a drooping speed-torque characteristic tosaid motor while overhauling in the lowering direction.

9. A variable voltage control system for a hoist motor comprising, incombination, a generator and motor each having a series field windingand a separately excited shunt field winding, said generator also havinga self excited shunt field winding, an external source of energizationfor said separately excited windings, reversing switch means foroperating said motor as an ordinary compound motor in the hoistingdirection and as a cumulative or differential compound motor in thelowering direction depending upon whether said motor is motoring oroverhauling,.respectively, so as to obtain a drooping speed-torquecharacteristic for the lowering, overhauling operation.

WALTER SCHAELCHIIN.

